Therapeutic device and system

ABSTRACT

Therapeutic devices that provide support or pressure to tissue. Devices contain a material that is capable of being contracted from its relaxed state to an evacuated state. The material applies pressure to the tissue of a patient when the material is in its relaxed state. Reduction of pressure by application of a vacuum results in a contracted state of the device, so that the device can be applied or delivered to a patient. Release of vacuum results in a return to the relaxed state, thus providing a maximum desirable pressure to tissue and avoiding the possibility of over-pressure which can result in tissue damage or necrosis.

FIELD OF THE INVENTION

The present invention relates to therapeutic devices and medicalappliances that provide support or pressure to tissue. In particular,the invention relates to devices and appliances comprising open cellfoam usefull in the treatment of diseases, disorders and injuries.

BACKGROUND OF THE INVENTION

Patients suffering from injury or disease or recovering from surgery maybe treated by the application of constant or intermittent pressure.Pressure is used to control swelling, increase blood flow, andimmobilize tissue.

In cases of acute injuries, such as acute joint injury, three treatmentsare employed simultaneously. First, the injured region is chilled (suchas with ice); second, pressure is applied using an elastic bandage; andthird, immobilization is achieved using a splint. For example, anathletic trainer applies elastic wrap to an injured ankle or knee andthen immobilizes the joint with a splint or bulky bandage. However, theapplication of elastic wrap may produce a wide range of pressures on theinjured limb. The incorrect pressure may retard venous or arterialcirculation and may contribute to thromboembolism; pressure that is toohigh can induce tissue ischemia that further injures the tissue.

More complex pressure devices are available to patients suffering fromvarious venous, circulatory and peripheral vascular diseases. Thesedevices typically consist of an inflatable bladder in the form of asleeve that can be placed around all or a portion of a patient's arm orleg. The bladder is connected to a pump that alternately inflates anddeflates the bladder. In some such devices, the sleeve placed around theextremity includes a number of sequential bladders along the axiallength of the sleeve to allow the sleeve to be inflated and deflated ina peristaltic manner along its length. By alternately inflating anddeflating the bladder or bladders contained within the sleeve,circumferential pressure is applied to the patient's extremity, thusaiding in the circulation of blood there through. Such systems arecurrently used to treat venous insufficiency, prevent deep venousthrombus and control lymphedema and improve tissue perfusion in patientswith peripheral arterial disease.

Other medical devices such as catheters and tracheotomy tubes are placedinto a body lumen and then held in place with an inflatable balloon atthe distal end of the device. The balloon is subject to over-inflation,however, again resulting in possible damage to treated tissue.

In addition, current systems tend to be expensive and complex,frequently being coupled to feedback circuits to control changes inpressure. Compression systems have been known to malfunction and causeundesirable variability in or increase in the applied pressure. Evenwhen such systems are controlled by the patient, they may be subject toincorrect operation resulting in over-inflation of the sleeve. For sucha system used to correct venous insufficiency in a limb, for example,incorrect operation is at best painful and at worst results in loss ofthe limb. Finally, most patients complain of some level of pain duringinflation due to the rapid increase in pressure against the extremity.

In view of the above, the need exists for therapeutic devices that arecapable of applying pressure but which are unable to produceover-pressure at the site of damage or disease. Such devices should besimple to use, allow peristaltic pumping at a variety of pressures, andhave the ability to apply heat or cold.

SUMMARY OF THE INVENTION

The present invention relates to therapeutic devices that providesupport or pressure to tissue. In particular, the invention relates tosuch devices comprising open cell foam useful in the treatment ofdiseases and injuries. The open cell foam is in a relaxed or relaxedstate until application of vacuum resulting in an evacuated state. Thefoam is engineered to produce a device that has characteristics thatprovide a maximum desirable pressure and that will avoid the possibilityof over-pressure which can result in tissue damage or necrosis.

In a first aspect, this invention is a medical device for applyingpressure to tissue comprising a body portion having a relaxed state anda contracted state, the body portion being configured to apply pressureto tissue in the relaxed state, the body portion adapted to contain afluid; and a fluid controller fluidly connected to the body portion forremoving fluid contained in the body portion, the body portion beingconfigured to contract from the relaxed state to the contracted stateupon removal of fluid from the body portion. The body portion maycomprise foam and preferably comprises open cell foam. The body portionalso may include a fluid impermeable outer coating. The medical devicemay also comprise a fluid source and a valve, the valve being connectedbetween the body portion and the fluid source and fluid controller, thevalve having a first position for connecting the body portion to thefluid controller and a second position for connecting the body portionto the fluid source. The fluid controller may be a vacuum source. Thevalve preferably is programmable and the valve may be programmed toswitch between the first position and the second position. The medicaldevice may comprise a bladder fluidly connected to a liquid wherein theliquid is hot or cold.

In a second aspect, this invention is a medical device for applyingpressure to a human or animal limb comprising a body portion having asubstantially cylindrical shape sized to fit over the limb, the bodyportion being adapted to contain a fluid and further having a relaxedstate and a contracted state, the body portion being configured to applypressure to the limb in the relaxed state, and a fluid controllerfluidly connected to the body portion for removing fluid contained inthe body portion, the body portion being configured to contract from therelaxed state to the contracted state upon removal of fluid from thebody portion. The body portion may comprise open cell foam and mayinclude a fluid impermeable outer coating.

In a third aspect, this invention is a medical device for applyingpressure to tissue comprising a body portion having at least twoseparate compartments, each compartment having a relaxed state and acontracted state and being configured to apply pressure to tissue in therelaxed state, the compartments being adapted to contain a fluid, and afluid controller fluidly connected to each compartment of the bodyportion for removing fluid contained in the body portion, eachcompartment being configured to contract from a relaxed state to acontracted state upon removal of fluid from the compartment. The devicemay include valves, the valves being connected between each compartmentand the fluid source and fluid controller and having a first positionfor connecting the compartment to the fluid controller and a secondposition for connecting the compartment to the fluid source. Eachcompartment may be separately cycled between the first and secondposition of the at least one valve in a sequence so as to apply pressureto tissue in a peristaltic manner.

In a fourth aspect, this invention is a medical device for applyingpressure to tissue comprising a body portion having a first regionconfigured to apply a first pressure to tissue and a second regionconfigured to apply a second pressure to tissue, each region having arelaxed state and a contracted state and capable of applying pressure totissue in the relaxed state, the regions being adapted to contain afluid, a fluid controller fluidly connected to the body portion forremoving fluid contained in the body portion, each region beingconfigured to contract from a relaxed state to a contracted state uponremoval of fluid from the compartment, wherein the first pressure is notequal to the second pressure. The pressure of the first and secondregions may form a gradient.

In a fifth aspect, this invention is a method of applying pressure totissue comprising supplying, adjacent to the tissue, a device having abody portion, the body portion having a fluid impermeable exterior and afluid containing interior; applying vacuum to the interior of the bodyportion to remove the fluid such that the body portion is in acontracted state; and removing the vacuum to the interior of the bodyportion to allow fluid to enter the interior such that the body portionis caused to expand to a relaxed state, the body portion in the relaxedstate applying pressure to the adjacent tissue. The pressure may bealternately applied and removed from the tissue.

In a sixth aspect, this invention is a method of supporting a patient'sbody in a bed or chair comprising supplying a patient supportingstructure having a plurality of compartments, each compartment having afluid impermeable outer portion and a fluid containing inner portion;applying a vacuum to the inner portion of a first compartment such thatthe first compartment is in a contracted state and pressure between afirst portion of the patient's body and the outer portion of the firstcompartment is reduced; removing the vacuum from the inner portion ofthe first compartment such that the first compartment is caused toexpand to a relaxed state such that increased pressure is applied to thefirst portion of the patient's body by the outer portion of the firstcompartment; applying a vacuum to the inner portion of a secondcompartment such that the second compartment is in a contracted stateand pressure between a second portion of the patient's body and theouter portion of the second compartment is reduced; removing the vacuumfrom the inner portion of the second compartment such that the secondcompartment is caused to expand to a relaxed state such that increasedpressure is applied to the second portion of the patient's body by theouter portion of the second compartment; and cycling between theapplying steps and the removing steps in the first and secondcompartments so that the pressure applied to the first and secondportion s of the patient's body is varied.

In a seventh aspect, this invention is a method of holding a medicaldevice in place in a body lumen comprising providing a device having asupport element in communication with a fluid line; the support elementhaving a relaxed state at ambient pressure and a contracted state atreduced pressure; removing fluid from the support element to produce thecontracted state; advancing the device through the lumen with thesupport element in the contracted state; positioning the device at adesired location within the body lumen; and admitting fluid at ambientpressure to the support element, thus returning the support element tothe relaxed state, the support element in the relaxed state beingconfigured to provide pressure against the body lumen to hold themedical device in place.

In an eighth aspect, this invention is a medical device comprising abody portion comprising a material adapted to contain a fluid, thematerial having a first size when filled with the fluid and a secondsmaller contracted size when the fluid is removed, the material beingselected to be in a relaxed condition when filled with fluid and toresist contraction to the second size when fluid is removed; and a fluidcontroller fluidly connected to the body portion, the fluid controllerbeing configured to remove fluid from the body portion.

The therapeutic device of this invention offers numerous advantages overdevices currently in use. The maximum compressive force that can beapplied to a patient's tissue is the force applied by the open cell foamin its relaxed state. By a proper selection of a foam with specificphysical characteristics, it is possible to predetermine the amount offorce to be applied to a patient's limb, and thereby prevent discomfort,pain and injury that can occur by providing excess pressures to a limbor body tissue. As such, the devices of this invention do not causediscomfort or injury to the patient due to malfunction or improperoperation. In addition, the present invention provides a simple andinexpensive way of achieving a peristaltic action on the limb of apatient suffering from circulatory or a peripheral vascular disease.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1E illustrate the expansion and evacuation cycles of devicesof the present invention.

FIG. 2 is a thickness versus pressure graph of the open cell foam usedin a preferred embodiment of this invention.

FIG. 3 is an illustration of a multi-pressure device on a patient's leg.

FIG. 4 is an illustration of a single pressure device on a patient'slower leg.

FIG. 5 is an illustration of a device on the plantar surface of thefoot.

FIG. 6A is an illustration of an ankle injury device and

FIG. 6B is a cross-sectional view of a portion of the device of FIG. 6A.

FIG. 7A is an illustration in longitudinal cross-section of a catheterand

FIG. 7B is an illustration in transverse cross-section of the catheterof FIG. 7A.

FIG. 8 is an illustration of a foam support device.

FIG. 9 is a diagrammatic view of a portion of a human vascular systemdepicting an abdominal aortic aneurysm in which a stent and foam deviceis deployed.

DETAILED DESCRIPTION OF THE INVENTION

The devices of this invention comprise a body portion made of a materialthat is capable of being contracted from its relaxed or resting state toan evacuated or contracted state. “Relaxed state” refers to thecondition of the material when no external forces are acting on it tocause the material to expand or contract. The evacuated or contractedstate of the material is produced by removal of fluid contained withinthe material. The terms “evacuated” and “contracted” refer to theapplication of vacuum on the material resulting in a reduction ofpressure within the material as compared to ambient pressure. Vacuum canbe applied by means of various pumps, aspirators, and suction devices.

Any material that is capable of being contracted from a relaxed state toan evacuated state may be used in the devices of this invention.Preferably, the material is an engineered open cell foam. A piece of theopen cell foam in a relaxed state is larger than the same piece in anevacuated state. In its relaxed state, the open cell foam is at ambientpressure; that is, the pressure inside the foam is that same as thatoutside the foam. The open cell foam is in a relaxed state untilapplication of vacuum (for example, due to suction from a wateraspirator or from a syringe), resulting in an evacuated state. The foamis designed to apply a desired pressure to the tissue of a patient inits relaxed state. One such suitable foam is commercially available fromNew Dimension Industries, Inc., of Moonachie, N.J., under thedesignation “2000 YELLOW”.

FIG. 1A illustrates the relaxed state of a material used for the medicaldevices of this invention. Foam 10 is covered with generally impermeablejacket or covering 12. This enables the body portion to assume andmaintain a contracted, evacuated state when air is evacuated from thefoam. Vacuum line 14 permits communication of air and vacuum with thefoam. Vacuum line 14 is fitted with valve 16 which connects the foam toeither vacuum source 15 or air/fluid source 17. Air/fluid source 17 maysimply be open line 14 to the atmosphere or may be a line to a source offluid, such as water. This may be a manual valve, such as a gate valve,controllable by a patient or physician, or it may be a solenoid valvethat can be programmed to cycle the foam between the relaxed andevacuated states. FIG. 1B shows the valve open to vacuum resulting inevacuated state 10. FIG. 1C shows foam 10 positioned near tissue T thatis to undergo treatment. FIG. 1D shows relaxed state foam 10 creating apressure against the tissue. FIG. 1E shows the next step in the cycle,i.e., evacuation state of foam 10.

Devices of this invention use the ability of the foam to cycle betweenrelaxed and evacuated states to treat circulatory disorders (e.g.,venous insufficiency and peripheral arterial disease), to immobilizeinjured limbs, and to stabilize (i.e., hold in place) catheters, shunts,and the like to body lumens. For treatment of a limb, for example, agenerally cylindrical device is fitted over the limb with the foam inthe evacuated state. Air is admitted into the foam, resulting in anincrease in size of the foam and application of pressure on the limb.For treatment of circulatory disorders, the foam cycles through therelaxed and evacuated state, thus stimulating venous flow of blood evenin the absence of muscular action. Similarly, the foam can be used indevices wherein the foam is constrained to expand in one direction only,such as in an eye-patch. Devices comprising the foam may also be used inbody lumens. The foam is an aid in positioning and holding in place, forexample, catheters, intravenous tubing, and wire leads from electrodesby delivering and positioning the device with the foam in an evacuatedstate. The foam is returned to its relaxed state to apply a constant,desired pressure to the body lumen. The possibility of over-pressure,such as with conventional balloons, is avoided since the maximumpressure which is applied by the foam is a function of the materialcomprising the foam. The devices may also be used in blood vessels,during the positioning of a stent or shunt, and may be used totemporarily occlude the flow of blood. The foam in its relaxed state isengineered to have characteristics that provide a maximum desirablepressure to the tissue undergoing treatment. The devices are designed toavoid the possibility of over-pressure which can result in tissue damageor necrosis.

In a preferred embodiment, the foam comprises an open cell structure,although the foam may include some closed cells. The foam is capable ofbeing reduced in size when air or other fluid is removed from the voids.This evacuated foam is capable of returning to its original size whenair or other fluid is admitted into the foam. That is, admission of afluid results in a restoration of the relaxed state of the foam. Vacuumis established by the application of vacuum in the foam by placing thefoam in communication with a vacuum or suction source and preventing airor other fluid from entering the foam. This can be done by placing thefoam within an impermeable, or air-tight, covering or coating. Thisvacuum source could be a vacuum pump or water aspiration. An emptysyringe could also be used to produce sufficient vacuum, particularlyfor small devices.

Various open cell foams are known in the art and are described in, forexample, Chapter 1 of “Low Density Cellular Plastics”, ed. N. C. Hilyardand A. Cunningham, Chapman & Hall, 1994. Various sizes, shapes, anddiameters of voids are present throughout an open cell foam. The opencell foam may also have some closed cells as artefacts of amanufacturing process or may be introduced as a way to control thecharacteristics of the foam. Such characteristics include the rate ofreturn and the thickness increase from evacuated to relaxed state. Inany event, fluid moves freely throughout the open cell foam, even in thepresence of some closed cells. This is in contrast to a closed cellfoam, in which the movement of fluid is not possible.

The foam used in the devices of this invention may have constantcharacteristics throughout the entire device, a gradient through thelength of the device, or regions with different characteristics. Thatis, for example, in a sleeve positioned on a limb, it may be desirableto have the thickness, response time, percentage of closed voids, etc.,vary along the length of the sleeve. Such variability in a sleeve can beuseful in helping to provide pumping action to the blood in the limb.

FIG. 2 is a graph illustrating how the pressure applied by an engineeredopen cell foam varies with the thickness of the foam. This graph wasobtained by placing a 3 inch (7.6 cm) thick piece of open cell foambetween two plates, compressing the foam, and measuring the forceapplied by the compressed foam against the plates. For use in thisinvention, it is desirable that the open cell foam have a region in thepressure/thickness curve wherein the pressure varies very little over arelatively large thickness change. That is, as shown in FIG. 2, for a 3inch (7.6 cm) thick piece of foam compressed to thicknesses rangingbetween 2.0 and 2.75, the pressure ranges from about 28 to 24 mm Hg(3732.6 to 3199.4 Pa). This means that virtually the same pressure isbeing applied at these thicknesses when the foam is used in a device.The utility of this can best be exemplified by envisioning a devicedesigned to fit a leg. A useful device must conform to the contour ofthe leg and yet should apply fairly constant pressure over the entireleg. Too much pressure can cause tissue damage and too little pressureis insufficient to support the leg. The device of this invention can beengineered to apply the same pressure to the entire leg simply byshaping the foam to follow approximately the contours of the leg.

A way of defining the desired relationship between pressure andthickness for devices of this invention is as follows. The open cellfoam is compressed to different thicknesses, T1 and T2. When theabsolute value of T1 minus T2 equals 0.5 inches (1.25 cm), thecorresponding pressure difference preferably is less than 10 mm Hg(1333.1 Pa), more preferably less than 5 mm Hg (666.5 Pa), and mostpreferably less than 2 mm Hg (266.6 Pa). Where this region appears onthe pressure vs. thickness graph will vary depending upon thecharacteristics of the foam and the thickness of the foam in its relaxedstate. The important feature is that there is a region in the pressurevs. thickness curve that is relatively constant, i.e., near zero slope.

In the devices of this invention, the material (e.g., foam) is overlaidwith an air-tight or impermeable covering or wrapping. The covering alsomay be adhered to the foam, for example, laminated or by means ofadhesive. Suitable coverings are those that are both impermeable andsufficiently flexible to withstand many evacuation cycles without anycracking or damage; that is, preferably the covering remains impermeableand flexible during usage of the device. In addition, these coveringswill be in contact with a patient's tissue and so must be biocompatible,non-irritating, and/or non-abrasive. For devices that lie against apatient's skin, the covering is selected based on comfort to thepatient. In addition, the covering may undergo sterilization and shouldbe compatible with sterilizing procedures. Typically the devices aresterilized by means of ethylene oxide (EtO) or by gamma radiation, asknown to one of skill in the art.

Suitable impermeable coverings comprise polymeric fabrics and films, orcloth fabrics coated with a polymeric layer. One such suitable polymercoated fabric is a polytetrafluoroethylene (PTFE) coated nylon. PTFEalso is referred to under the trade designation TEFLON™ fabrics andfilms. Silicone-impregnated fabrics, nylon fabrics, and rubberizedfabrics are also suitable for use in the devices of this invention.

FIG. 3 illustrates another embodiment of the invention. This shows adevice for the treatment of circulatory disorders (e.g., venousinsufficiency) in a leg. It is to be understood that the device could beused on any limb or portion of limb that requires treatment. Device 30is designed to treat vascular or lymphatic disorders and comprises anopen cell foam in a generally cylindrical shape covered with animpermeable fabric. Inlets through the fabric permit fluid communicationwith the foam via vacuum/air lines. Device 30 has compartments 32, 34,36 and 38 connected to air and vacuum lines 33, 35, 37, and 39,respectively. Device 30 is fastened on the leg by means of fasteners 31a to 31 g. Lines 33, 35, 37 and 39 feed into fluid controller 25 whichsupplies vacuum and air by means of valves (not shown) to thecompartments as desired. Preferably, the controller is programmed tovary the supply of air and vacuum by means of the valves so that thepressure is applied to the limb in the desired sequence. When fittedaround a limb, device 30 forms a cylinder or sleeve having an axialpassageway extending through it. The thickness of the cylinder wallsrange from about 1.5 to 3 inches (about 3.8 to 7.6 cm). The exteriordiameter ranges from 6 to 10 inches (15.2 to 25.4 cm). The axial passageway additionally may be lined with a material which is comfortableagainst skin, such as polypropylene fabric. Other synthetic or naturalfabric may be used. By varying the pressure of each compartment up theleg in sequence, the return flow of blood is stimulated. This isparticularly useful after surgery or anytime that a patient isimmobilized and venous flow is compromised.

The compartments comprise desired thicknesses of the open cell foam asdescribed above, adapted to fit the desired portion of the leg and applythe desired pressure covered by an impermeable covering. The chamberseach independently communicate with a vacuum pump. There is nocommunication between chambers. Thus, it is possible for one foamchamber to be evacuated while adjacent chambers are in their relaxedstate. The compartments may be adjoined to each other or they may beseparate. Typically such a device is provided as a cylindrical sleeve.The sleeve typically has a longitudinal slit along its length. Thesleeve is placed around the patient's leg and then closures or fastenersare used to hold the sleeve in place. Such closures include strapscomprising hook and loop tape. Alternatively, the closure may comprisean outer shell material such as a fabric sheet that is wrapped entirelyaround the sleeve and sealed using buttons, zippers, adhesives, hook andloop fasteners, and the like. Nylon fabric is a useful material for anouter shell. Regardless of the closure method selected, the closure mustbe sufficiently strong to allow the sleeve in its relaxed state toprovide the desired pressure.

The device is placed on the leg (i.e., affixed with closures) with theopen cell foam in its evacuated state. Air is then admitted to eachcompartment in turn, beginning with foot compartment 32. Vacuum isapplied to foot compartment 32 as calf compartment 34 is allowed to fillwith air. In this manner, blood is forced up the leg even in the absenceof normal muscle activity. By selectively choosing which chambers areevacuated and which chambers fill with air, it is possible to alter thepressure along the leg. If the compartments are positioned along thelongitudinal axis of the sleeve and subjected to suction forces in asequential manner, peristaltic action occurs along the leg.

The device thus stimulates blood flow in the limb. The device isdesigned to cycle through many evacuation and filling cycles. Typically,treatments provide pressure to a limb for approximately 60 secondsfollowed a release of pressure lasting for times ranging from 30 to 60seconds. The pressure applied depends on the clinical situation. Forexample, most patients need a pressure of 30 to 50 mm Hg (3999.24 Pa to6665.4 Pa) for venous disease and deep vein thrombosis prevention, and apressure of 60 to 80 mm Hg (7998.5 Pa to 10664.6 Pa) for lymphedema.Thus, the thickness of the open cell foam in the compartments, as wellas the characteristics of the foam, are chosen to produce pressures andcycling times in the desired ranges.

FIG. 4 illustrates a device for use in immobilizing a limb and/or forthe treatment of circulatory disorders. Immobilization is particularlyuseful for treatment of acute injuries (e.g., sports injuries).Typically, for immobilization of a leg, the device would be onecompartment, provided in a roughly cylindrical shape with a longitudinalslit down its length. The open cell foam is in fluid communication withvacuum and air lines to produce evacuated and relaxed states of thefoam. The device would be placed on the limb of an injured person withthe open cell foam in an evacuated state. Once air is admitted (e.g., byopening a valve), the foam would return to its relaxed state, thusapplying pressure to the leg, controlling edema and also acting as asplint. Clearly, the pressure could be cycled with this device byalternately applying vacuum and admitting air. This invention providesthe desired pressure to the leg, and is engineered so that it cannotexceed the desired pressure and cause further damage to the tissue.

Device 40 comprises calf chamber 42 and foot chamber 44. Foot chamber 44articulates at the ankle. Chambers 42 and 44 are in communication withair and vacuum line 45, shown adjoining chamber 42. Line 45 is providedwith valve 49, in communication with air and vacuum sources (not shown)via lines 43 and 46. Valve 49 can be turned manually, or may be a 20microprocessor or controller which permits automatic flow of air andvacuum into the chambers. Device 40 is similar to device 30, describedabove, in that the thickness of the open cell foam varies depending uponthe part of the leg. The compartments are covered by an impermeablecovering. Device 40 forms a sleeve in use; a longitudinal slit along itslength permits positioning of the sleeve on the calf and foot. Hook andloop fasteners 47 a to 47 f hold the sleeve in place. Other types offasteners, such as snaps or zippers, could also be used.

FIG. 5 illustrates a device that provides intermittent pressure to thebottom, or plantar area, of the foot. This device is used when a patientis unable to walk, as for example, after surgery, and helps preventblood clots by causing blood to move up the leg. Device 50 comprisessingle compartment 52 in communication with air and vacuum sources (notshown) via line 55. Line 55 is provided with valve 59 that is turned toclose off the source of air to line 55 and provide vacuum via line 56.Valve 59 may be manually operated or may be a microprocessor or thelike. The open cell foam in the device is covered with impermeablecovering 53. The thickness of the foam for such a device ranges fromabout 0.5 inch (1.2 cm) to about 2 inches (5.1 cm). The device is placedat the plantar arch in an evacuated state. The open cell foam isengineered to produce fast recoil and a pressure ranging from 80 to 100mm Hg (10664.6 Pa to 13331 Pa). Typically, the device is in an evacuatedstate for 10 to 60 seconds and in its relaxed state for up to 5 seconds.This results in relatively brief bursts of pressure being applied to theplantar arch, resulting in the flow of blood up the calf.

FIG. 6A illustrates another device used for the treatment of acuteinjuries and shows such a device on an ankle. FIG. 6B shows across-section of the device along line a-b. Device 60 comprises opencell foam 62 covered with impermeable layer 63 which is fastened aroundthe foot and calf and held in place with closures, similar to thatdescribed for the device in FIG. 3. This device permits treatment of aninjured area with heat or cold by providing hot or cold liquid tobladder 64 via line 65. Valve 67 controls the admission of fluid to thebladder. FIG. 6A illustrates the bladder next to the skin of the patientbut the bladder could form the outermost layer of the device. The deviceis wrapped around the ankle when the foam is in the evacuated state. Thethickness of the foam is adjusted to adapt to the needed thickness forthe foot, ankle, and calf. Air is admitted to the foam via line 61 toreturn the foam to its relaxed state and apply pressure to the area. Amanual or microprocessor controlled valve 69 controls the admission ofair and vacuum. The temperature of the liquid is selected depending uponthe treatment desired. For example, for acute injury, it is frequentlydesirable to chill the area, to reduce swelling and tissue damage.Meanwhile, compression of the injury is also necessary to control edema.Device 60 is easily removed by unfastening the closures and applying avacuum to produce the evacuated state of the foam. Thus, removal of thedevice does not cause more damage to the limb. Though FIG. 6Aillustrates application of the device to an ankle, any body partsuffering acute injury could be treated in this manner. In particular,injuries to the neck and to joints such as the knee, wrist, elbow,fingers, and toes benefit from treatment with a device illustrated inFIG. 6A. Treatment of an injured neck with such a device is particularlyefficacious. For acute neck injuries, a patient typically is immediatelyimmobilized with a neck brace and then transported to a hospital forfurther care. Conventionally used neck braces are difficult to removeand further make it difficult to perform other necessary treatment, suchas a tracheotomy. Thus there is risk of further damage to a patient dueto the manner of immobilization. The device of this invention may beeasily loosened or removed once vacuum or suction (e.g., hospitalsuction) is applied.

Alternatively, rather than using a bladder or separate compartment tohold chilled fluid, a chilled liquid can be placed in communication withan inlet to the device when the foam is in its evacuated state. A valveopens and chilled fluid is drawn into the open cells of the foam. Thesleeve becomes chilled by the presence of the chilled fluid, therebyserving to cool the body part contained within the sleeve. At the sametime, the device is applying pressure to the body part, and, as shown inFIG. 6, immobilizing it. The liquid may be chilled by radiant cooling(i.e., refrigeration or immersion in ice water) or may be cooled as aresult of an endothermic chemical reaction. Likewise, if it is desiredto provide heat to the injured limb, a warm liquid can be provided, thatliquid being heated radiant heating, an exothermic chemical reaction orby electromagnetic energy (i.e., microwave energy). It is expected thatthe foam will provide some insulating effect, thereby maintaining thefluid, and thereby the sleeve, at a temperature within a desired rangefor a period of time sufficient to provide an initial therapeuticeffect.

FIGS. 7A and 7B illustrate the use of the open cell foam of thisinvention within a body lumen. A catheter in a body lumen is shown inlongitudinal cross-section in FIG. 7A with a positioning device at thedistal end of the catheter comprising the open cell foam and animpermeable covering. FIG. 7B shows the transverse cross-section of thecatheter in the region of the foam. FIG. 7A shows a body lumen L, suchas a blood vessel or a urethra, etc., having inserted in it catheter 70.Catheter 70 has a proximal end (that nearest the entry point of thedevice) 72 and a distal end 74. Near distal end 74 is open cell foam 76disposed in an annular arrangement around distal end 74. An impermeablecoating or covering 77 surrounds foam 76. The catheter is delivered withthe foam in an evacuated state. The foam is in fluid communication vialine 78 with a vacuum source (as, for example, a syringe; not shown) sothat it may be returned to its evacuated state for removal of thecatheter. Air or other fluid is admitted to the foam (either by separatecommunication with a source of fluid or through the catheter wall) andthe foam expands to hold the catheter 70 in place.

Similarly, such a device could be used to position a shunt between twosections of blood vessel. The shunt would be delivered to the bloodvessel with the foam in the evacuated state. Upon admission of air orother fluid, the foam returns to its relaxed state, thus pressingagainst the walls of the blood vessel and holding the shunt in place.The foam could also be used for vessel occlusion. Suction provided bysyringe would be sufficient to remove air or other fluid from the foamand produce an evacuated state.

The devices of this invention can also be used in other body lumens,such as the esophagus, as an endotracheal tube. The advantage to such adevice is that the pressure applied to the esophagus when the foam ispermitted to return to its relaxed state would be unable to cause damageto tissue. That is, the foam would be engineered to provide the desiredpressure for a range of diameters. Different sizes of tubes would, ofcourse, be used depending upon the size of the patient's trachea (e.g.,children as compared to adults). Current techniques of securing suchtubes include using an inflatable balloon to hold the tube in place.These balloons need to be at a low pressure to prevent damage to thetrachea. Properly engineered foam would provide sufficient pressure toplace the tube with no danger of over-inflation, such as occurs whenusing the balloons.

FIG. 9 illustrates the placement of a stent in abdominal aortic aneurysmA. The aneurysm begins below the renal arteries RA but does not extendinto either of the common iliac arteries I. The stent spans the aneurysmand is seated at its cranial (i.e., near the head) portion 92 and caudalportion 94 by means of foam. Foam 96 also fills the region between thestent and the walls of the artery, providing support to the arterialwalls. The foam preferably would be covered or coated with material thatis biocompatible with the vasculature. The stent would be delivered tothe aneurysm with the foam in an evacuated state. The foam would beengineered so that the pressure at the cranial and caudal ends of thestent would be sufficient to assist in holding the stent in place. Thefoam filling the space between the stent and the arterial walls likelywould be engineered to apply less pressure than that engineered foreither the cranial or caudal ends of the stent.

It is also contemplated that a foam device could be used to occlude orembolize a vessel; for example, a blood vessel having an aneursym,particularly in the brain. Current treatments of brain aneurysms includeinserting a balloon into an aneurysm; potential problems with thisinclude loss of pressure of the balloon, rendering it ineffective. Afoam device could not deflate, and the foam would be engineered toprovide the proper pressure to the vessel walls.

Foam support devices are contemplated to be useful in other bodycavities, such as that which may be created during surgery, as, forexample, during a mastectomy. Such devices fill the space created andmay help prevent fibrous growth as well as excess drainage.Alternatively, a foam device could be engineered to function as ascaffold to support tissue growth into a body cavity.

Another use of the foam support device is in a penile implant. Currentinflatable penile implants use two or three inflatable cylindersimplanted into the corpora cavernosa of the penis. A reservoircontaining a fluid (e.g., saline) and a pump are implanted into thescrotum and/or abdomen. Erection is accomplished by pumping saline intothe cylinders from the reservoir. To return the penis to a flaccidstate, pressure is applied manually to the penis while a valve isactuated allowing the fluid to be forced back into the reservoir.

The foam of this invention, encased in a fluid-tight sheath, could beused in place of the inflatable cylinders. The foam could utilize areservoir for the fluid but a pump would not be needed. Actuating avalve would permit fluid (e.g., air) in the reservoir to flow and allowthe foam to expand to a predetermined state. To return to the flaccidstate, pressure would be applied manually to the penis while the valveis open, forcing fluid into the reservoir, then the valve would beclosed.

Advantages to the use of an engineered foam for a penile implant includethe inability to over-inflate the implant (which possibly results inrupture), the ability to use either a gaseous or liquid fluid to expandthe foam, and reduction in system complexity by not requiring a pump.

The foam of this invention is also contemplated for use in a supportdevice, such as a bed or chair, as illustrated in FIG. 8. In thisexample, compartments 82 a to 82 g are in communication with air andvacuum via lines 84 a to 84 g. The admission of air and vacuum iscontrolled by valves 86 a to 86 g such as those described above.Preferably the variation of pressure provided by the support surface tothe patient is varied automatically, such as controlled by a computer.This device prevents bed sores and pressure ulcers, such as happen whena patient cannot move for long periods of time. The use of open cellfoam along with application of alternating vacuum and admission of airprovides a device in which the pressure can be varied to prevent damageto tissue.

In each of the embodiments discussed above, it has been assumed that thematerial comprising the body portion automatically returns to itsrelaxed state upon release of an external force (e.g., vacuum). Whilethis constitutes one preferred embodiment, it is to be understood that,that is not the only way by which the material may achieve its expanded,relaxed state. In particular, positive pressure could be provided to thematerial causing the material to expand to its predetermined relaxedstate, or, in the embodiment in which a heated or chilled liquid isprovided, the liquid may be provided under pressure to thereby returnthe material to its relaxed state. Regardless of the type of expansionforce used, however, it is intended that the device be selected suchthat it provides a maximum, predetermined compression force to thepatient's limb when the material is expanded. Unlike conventionalcompression systems that employ a bladder, it is intended that therelaxed state of the material places the material in its maximum volumeconfiguration, thereby preventing over-inflation or over-pressure.

Although particular embodiments have been disclosed herein in detail,this has been done for purposes of illustration only, and is notintended to be limiting with respect to the scope of the claims. Inparticular, it is contemplated that various substitutions, alterations,and modifications may be made to the invention without departing fromthe spirit and scope of the invention as defined by the claims. Forinstance, the composition of materials is believed to be a matter ofroutine for a person of ordinary skill in the art with knowledge of theembodiments disclosed herein.

What is claimed is:
 1. A medical device for applying pressure to tissuecomprising: a body portion having an expanded position and a contractedposition, the body portion being in a relaxed state when in the expandedposition, the body portion being configured to apply a therapeuticallyeffective amount of pressure to tissue in the relaxed state, the bodyportion adapted to contain a fluid; and a fluid controller fluidlyconnected to the body portion for removing fluid contained in the bodyportion, the body portion being configured to contract from the expandedposition to the contracted position upon removal of fluid from the bodyportion.
 2. The medical device of claim 1 wherein the body portioncomprises foam.
 3. The medical device of claim 2 wherein the bodyportion comprises open cell foam.
 4. The medical device of claim 1wherein the body portion includes a fluid impermeable outer coating. 5.The medical device of claim 1 further comprising a fluid source and avalve, the valve being connected between the body portion and the fluidsource and fluid controller, the valve having a first position forconnecting the body portion to the fluid controller and a secondposition for connecting the body portion to the fluid source.
 6. Themedical device of claim 1 wherein the fluid controller is a vacuumsource.
 7. The medical device of claim 5 wherein the valve isprogrammable.
 8. The medical device of claim 7 wherein the valve isprogrammed to switch between the first position and the second position.9. The medical device of claim 1 further comprising a bladder fluidlyconnected to a liquid wherein the liquid is hot or cold.
 10. A medicaldevice for applying pressure to a human or animal limb comprising: abody portion having a substantially cylindrical shape sized to fit overthe limb, the body portion being adapted to contain a fluid and furtherhaving an expanded position and a contracted position, the body portionbeing in a relaxed state when in the expanded position, the body portionbeing configured to apply a therapeutically effective amount of pressureto the limb in the relaxed state, and a fluid controller fluidlyconnected to the body portion for removing fluid contained in the bodyportion, the body portion being configured to contract from the expandedposition to the contracted position upon removal of fluid from the bodyportion.
 11. The medical device of claim 10 wherein the body portioncomprises open cell foam.
 12. The medical device of claim 10 wherein thebody portion includes a fluid impermeable outer coating.
 13. The medicaldevice of claim 10 further comprising a fluid source and a valve, thevalve being connected between the body portion and the fluid source andfluid controller, the valve having a first position for connecting thebody portion to the fluid controller and a second position forconnecting the body portion to the fluid source.
 14. The medical deviceof claim 13 further comprising a cooling member to cool the fluid in thefluid source.
 15. The medical device of claim 13 further comprising aheating member to heat the fluid in the fluid source.
 16. The medicaldevice of claim 13 wherein the valve is programmable.
 17. The medicaldevice of claim 16 wherein the valve is programmed to switch between thefirst position and the second position.
 18. A medical device forapplying pressure to tissue comprising: a body portion having at leasttwo separate compartments, each compartment having an expanded positionand a contracted position, each compartment being in a relaxed statewhen in the expanded position, and being configured to apply atherapeutically effective amount of pressure to tissue in the relaxedstate, the compartments being adapted to contain a fluid, and a fluidcontroller fluidly connected to each compartment of the body portion forremoving fluid contained in the body portion, each compartment beingconfigured to contract from the expanded position to the contractedposition upon removal of fluid from the compartment.
 19. The medicaldevice of claim 18 wherein the body portion comprises open cell foam.20. The medical device of claim 18 wherein the body portion includes afluid impermeable outer coating.
 21. The medical device of claim 18further comprising valves, the valves being connected between eachcompartment and the fluid source and fluid controller and having a firstposition for connecting the compartment to the fluid controller and asecond position for connecting the compartment to the fluid source. 22.The medical device of claim 21 wherein the at least two valves areprogrammable.
 23. The medical device of claim 22 wherein the at leasttwo valves is programmed to switch between the first position and thesecond position.
 24. The medical device of claim 21 wherein eachcompartment is separately cycled between the first and second positionof the at least one valve in a sequence so as to apply pressure totissue in a peristaltic manner.
 25. A medical device for applyingpressure to tissue comprising: a body portion having a first regionconfigured to apply a first pressure to tissue and a second regionconfigured to apply a second pressure to tissue, each region having anexpanded position and a contracted position, each of the first andsecond regions being in a relaxed state when in the expanded position,and being capable of applying a therapeutically effective amount ofpressure to tissue in the relaxed state, the regions being adapted tocontain a fluid, a fluid controller fluidly connected to the bodyportion for removing fluid contained in the body portion, each regionbeing configured to contract from the expanded position to thecontracted position upon removal of fluid from the compartment, whereinthe first pressure is not equal to the second pressure.
 26. The medicaldevice of claim 22 wherein the pressure of the first and second regionsforms a gradient.
 27. A method of applying pressure to tissuecomprising: supplying, adjacent to the tissue, a device having a bodyportion, the body portion having a fluid impermeable exterior and afluid containing interior; applying vacuum to the interior of the bodyportion to remove the fluid such that the body portion is in acontracted state; and removing the vacuum to the interior of the bodyportion to allow fluid to enter the interior such that the body portionis caused to expand to a relaxed state, the body portion in the relaxedstate applying a therapeutically effective amount of pressure to theadjacent tissue.
 28. The method of claim 27 further comprisingalternately applying and removing vacuum to the interior of the bodyportion such that pressure is alternately applied and removed from thetissue.
 29. A method of supporting a patient's body in a bed or chaircomprising: supplying a patient supporting structure having a pluralityof compartments, each compartment having a fluid impermeable outerportion and a fluid containing inner portion; applying a vacuum to theinner portion of a first compartment such that the first compartment isin a contracted state and pressure between a first portion of thepatient's body and the outer portion of the first compartment isreduced; removing the vacuum from the inner portion of the firstcompartment such that the first compartment is caused to expand to arelaxed state such that increased pressure is applied to the firstportion of the patient's body by the outer portion of the firstcompartment; applying a vacuum to the inner portion of a secondcompartment such that the second compartment is in a contracted stateand pressure between a second portion of the patient's body and theouter portion of the second compartment is reduced; removing the vacuumfrom the inner portion of the second compartment such that the secondcompartment is caused to expand to a relaxed state such that increasedpressure is applied to the second portion of the patient's body by theouter portion of the second compartment; and cycling between theapplying steps and the removing steps in the first and secondcompartments so that the pressure applied to the first and secondportions of the patient's body is varied.
 30. A medical device forapplying pressure to tissue comprising: a body portion having a relaxedposition and a contracted position, the body portion being configured toapply a therapeutically effective amount of pressure to tissue in therelaxed position, the body portion having an exterior surface and aninterior portion adapted to contain a fluid; and a vacuum sourceconnected to the interior portion of the body portion for removing fluidcontained in the body portion, the body portion being configured tocontract from the relaxed position to the contracted position uponremoval of fluid from the body portion.
 31. The medical device of claim30 wherein the body portion comprises open cell foam.
 32. The medicaldevice of claim 1 wherein the body portion includes a fluid impermeableouter coating.
 33. A medical device for applying pressure to a human oranimal limb comprising: a body portion having a substantiallycylindrical shape sized to fit over the limb, the body portion beingadapted to contain a fluid and further having a relaxed position and acontracted position, the body portion being configured to apply atherapeutically effective amount of pressure to tissue in the relaxedposition, and a vacuum source connected to the interior portion of thebody portion for removing fluid contained in the body portion, the bodyportion being configured to contract from the relaxed position to thecontracted position upon removal of fluid from the body portion.
 34. Themedical device of claim 33 further comprising a fluid source and avalve, the valve being connected between the body portion and the fluidsource and vacuum source, the valve having a first position forconnecting the body portion to the vacuum source and a second positionfor connecting the body portion to the fluid source.
 35. The medicaldevice of claim 34 further comprising a cooling member to cool the fluidin the fluid source.
 36. A medical device for applying pressure totissue comprising: a body portion having at least two separatecompartments, each compartment having a relaxed position and acontracted position, the body portion being configured to apply atherapeutically effective amount of pressure to tissue in the relaxedposition, the compartments being adapted to contain a fluid, and avacuum source connected to the interior portion of the body portion forremoving fluid contained in the body portion, the body portion beingconfigured to contract from the relaxed position to the contractedposition upon removal of fluid from the body portion.
 37. A medicaldevice for applying pressure to tissue comprising: a body portion havinga first region configured to apply a first pressure to tissue and asecond region configured to apply a second pressure to tissue, eachregion having a relaxed position and a contracted position, the bodyportion being configured to apply a therapeutically effective amount ofpressure to tissue in the relaxed position, the regions being adapted tocontain a fluid; and a vacuum source connected to the interior portionof the body portion for removing fluid contained in the body portion,the body portion being configured to contract from the relaxed positionto the contracted position upon removal of fluid from the compartment,wherein the first pressure is not equal to the second pressure.
 38. Themedical device of claim 37 wherein the pressure of the first and secondregions forms a gradient.